The invention relates generally to the field of power electronic devices such as those used in power conversion or for applying power to motors and other loads. More particularly, the invention relates to devices such as motor drives with an improved choke which provides improved protection from the environment.
In the field of power electronic devices, a wide range of circuitry is known and currently available for converting, producing and applying power to loads. Depending upon the application, such circuitry may convert incoming power from one form to another as needed by the load. In a typical arrangement, for example, constant (or varying) frequency alternating current power (such as from a utility grid or generator) is converted to controlled frequency alternating current power to drive motors, and other loads. In this type of application, the frequency and voltage of the output power can be regulated to control the speed of the motor or other device. Many other applications exist, however, for power electronic circuits that convert alternating current power to direct current power, or vice versa, or that otherwise manipulate, filter, or modify electric signals for powering a load. Circuits of this type generally include rectifiers (converters), inverters, and power conditioning circuits. For example, a motor drive will typically include a rectifier that converts AC voltage to DC. Inverter circuitry then converts the DC voltage into an AC voltage of a particular frequency desired for driving a motor at a particular speed. Often, power conditioning circuits, such as a choke and/or a bus capacitor are used to remove unwanted voltage ripple on the internal DC bus. Depending on the power load, the power conditioning circuits, such as the choke, may conduct very high levels of current and generate significant levels of heat.
To dissipate the heat generated by the circuitry of the motor drive, the motor drive unit will typically include a cooling channel that conducts cooling air through a heatsink thermally coupled to the semiconductor circuits described above. To make efficient use of the space within the motor drive unit, the choke is usually deployed within this cooling channel. Furthermore, the motor drive may be deployed such that the cooling channel is exposed outside of the equipment cabinet. Thus, the choke may be subject to dust and water.
Therefore, it may be advantageous to provide a motor drive unit with an improved choke that is protected from the environment. In particular, it may be advantageous to provide a choke with improved protection from water and dust.